Boat propulsion unit

ABSTRACT

Boat propulsion unit comprising a suspension arrangement (2) and a propeller drive shaft housing (3) which, via a lower and an upper universal joint (22, 24, respectively), are pivotally connected to each other. The suspension arrangement comprises a frame (5) in the form of an extruded aluminum profile which is fixed around an opening in a boat transom, and a carrier (6) attached to the frame member, the carrier covering the opening and supporting the pivot connection. The carrier is integrally formed with a flywheel casing (20) for a connected engine.

FIELD OF THE INVENTION

The present invention relates to a boat propulsion unit intended to besuspended on the outside of a boat transom and driveably connected to anengine on the inside of the transom. Such unit comprises a propellerdrive shaft housing, a suspension arrangement intended to be fixedlysecured to the transom, pivot means which pivotally connect the driveshaft housing to the suspension arrangement to allow pivotaldisplacement of the drive shaft housing relative to the suspensionarrangement about a pivot axis in a vertical plane and a pivot axis inhorizontal plane, steering means which is arranged to effect pivotaldisplacement of the drive shaft housing about the first-mentioned axis,and trim and tilt means which is arranged to effect pivotal displacementof the drive shaft housing about the second-mentioned axis.

BACKGROUND OF THE INVENTION

Conventional boat propulsion units of the above-mentioned type, forexample so-called Aquamatic® drive units, incorporate a carrier screwedto the boat transom. The propeller drive shaft housing is suspended fromthe carrier by means of a forked bracket which is pivotable about ahorizontal transverse axis accommodated in the carrier. A substantiallyvertical steering axis or spindle is connected to the drive shafthousing and is journalled in the forked bracket. A steering armcooperates with the spindle. The steering mechanism of the boat, forexample a push-pull cable or a servo unit, acts on the steering arm inorder to cause its displacement and thereby that of the propeller driveshaft housing. Trimming and tilting of the drive shaft housing isachieved by pivoting the forked bracket upwardly. This is normallycarried out with the help of a pair of hydraulic cylinder arrangements,with one hydraulic cylinder acting on each leg of the forked bracket.

SUMMARY OF THE INVENTION

It is a general object of the present invention to provide a boatpropulsion unit which can be produced at a considerably lower cost thanpropulsion units of the above-described known type and which, inaddition, is simpler to install on a boat.

This is achieved in accordance with the present invention by means ofthe suspension arrangement comprising a frame member which is intendedto be fixed around an opening in a boat transom, and a carrier attachedto the frame member and shaped so that it forms a flywheel casing for anengine, said carrier covering the opening and supporting said pivotmeans.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages attained by the invention will be apparent from the followingdescription and with reference to the embodiment shown in the attacheddrawings, of which

FIG. 1 shows a schematic partial sectional view of a boat propulsionunit according to the invention, and

FIG. 2 is an enlargement of the region II of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, reference numeral 1 generally denotes a boat propulsion unitof the so-called INU-type, for example an Aquamatic®-drive unit, whichconsists of two main components, namely a suspension arrangement 2 and apropeller drive shaft housing 3.

The suspension arrangement 2 consists of two main parts, i.e. a framemember 5 affixed to a boat transom 4 and an inner carrier supported bythe frame member 5. The frame member 5 is an extruded aluminum profile,which presents a hollow cavity 7 that can be used for various purposes.For example, the cavity can be used to conduct exhaust gases and coolingwater from an engine 8 connected to the propulsion unit 1, whereby thecavity presents an inlet (not shown) and an outlet 9 for the coolingwater and the exhaust gases. Alternatively, the frame member 5 can beused as a cooler for various fluids, for example engine oil, whereby thelubrication system of the engine communicates via not shown inlets andoutlets with the cavity 7 in the frame member 5.

The aluminum profile which forms the frame member 5 is provided with aU-shaped slot 10 in which a seal 11 is inserted. The frame member 5 isaffixed to the outside of the boat transom 4 so that the seal 11surrounds and seals against the edge of an opening 12 in the transom 4.To achieve this, the profile 5 is provided with a T-shaped slot 13within which a plurality of screws 14 having heads. adapted to the shapeof the slot 13 project. Each screw 14 extends through an opening in aU-shaped yoke 15 and clamps one leg 15a of the yoke against the edge ofthe opening 72 by means of a nut 16. The other leg 15b of the yokeprojects into a shallow slot 17a in a covering ring 17, this ringforming the one delimitation of a U-shaped channel 18 in which a ring 19of flexible material is accommodated. The ring 19 presents a slot 19ainto which an edge region of the inner carrier 6 projects, so that adamped suspension of the inner carrier 6 is achieved in the frame member5.

The described arrangement provides for a very simple mounting of thesuspension arrangement 2 of the drive shaft housing 3. The profile 5 ispresented to the outside of the transom with the yokes 15 looselycarried on the screws 14 and turned through 90° from the position shownin the drawings. After inserting the inner carrier 6 with the dampingring 19 in the channel 18 and applying the covering ring 17, the yokes15 are rotated to the position showed in the drawings, whereafter thenuts 16 are tightened. The inner carrier 6 is now attached andresiliently supported within the opening 12 in the transom. The driveassembly consisting of the cooperating engine and propulsion unit herebyhas a common center of gravity which is located a short distance fromthe plane of the damping ring 19. This implies that the need for furtherengine mountings is avoided.

The inner carrier 6 is shaped so that it forms a flywheel casing 20 forthe connected engine 8. A cylinder 21 for a lower ball-type universaljoint, generally denoted by 22, and a seat 23 for an upper ball-typeuniversal joint, generally denoted by 24, is formed integrally in theshown embodiment with the inner carrier 6, though may also be in theform of separate components fixedly attached to the carrier. This alsoapplies for the flywheel casing 20.

The lower ball-joint 22 has a ball 25 which is rigidly connected to thedrive shaft housing 3 via a neck 26 and is accommodated in a sphericalrecess in a piston member 27. The piston member 27 is displaceable inthe cylinder 21 against the action of a helical spring 28 accommodatedin the cylinder. The ball 25 and the neck 26 present a through-passage29 which communicates with a passage 30 in the drive shaft housing 3.The passage 30 is in communication with a cooling water inlet 31 in theunderwater casing 32 of the drive shaft housing.

The upper ball-joint 24 has a ball 33 which is fixedly attached to ahydraulic cylinder 34 of a hydraulic piston-cylinder arrangement,generally denoted by 35. The piston rod 37 of the piston-cylinderarrangement displaceably extends through a bore 38 in the ball 33. Thepiston rod 37 extends forwardly and rearwardly from the ball joint 24and towards an upper region 38 of the drive shaft housing 3 and, at itsremote end, carries a forked bracket 39 which is clamped to the driveshaft housing region 38. The legs 40 (only one of which is shown) of theforked bracket 39 are pivotally connected via pivot pins 41 to the driveshaft housing region 38 to thereby permit pivotal displacement about thepivot pins 41. The cylinder 34 presents a pair of attachment rings 42 towhich a not-shown steering mechanism, for example a push-pull cable or aservo unit, of a type known per se is intended to be connected in orderto convert displacement of the steering wheel into sideways pivotaldisplacement of the piston-cylinder arrangement 35.

During pivotal displacement of the arrangement 35 about an axis "a"lying in a vertical plane by means of the steering mechanism, the driveshaft housing 3 is swung sideways, corresponding to displacement of aconventional drive shaft housing which has a steering spindle withsteering arm journalled to a forked bracket. The hydraulic arrangement35 thus serves as a tiller. When hydraulic oil is supplied to thecylinder space 43 of the cylinder 34 from a hydraulic pump 44, the driveshaft housing 3 is displaced about a horizontal axis "b" for trimming ortilting of the rig. The hydraulic arrangement consequently also servesas a trim-cylinder and tilt-cylinder. The double trim-cylinders and thesteering arm of the known propulsion unit described earlier are herebyreplaced by a single piston-cylinder arrangement 35 which, incombination with the embodiment of a forked bracket 39 on an angledcylinder arrangement 35, provides high stability whilst ensuring thatthe drive shaft housing not only can be trimmed, but also can be tiltedupwardly by a necessary amount, for example 45°.

As described above, by means of conducting cooling water through thelower ball 25, the need for a separate cooling water conduit between thedrive shaft housing and the engine is eliminated. Ram pressure createdby water flowing into the cooling water inlet 31 in the drive shafthousing 3 is dependent on the speed of the boat and will act in thecylinder space 45 of the cylinder 21. This pressure acts together withthe spring arrangement 29 in a direction opposite to the propellerpressure force. The spring force can be balanced against the propellerpressure force so that the ram pressure can be used to provide automatictrimming of the drive shaft housing 3 as the speed increases. This isachieved by means of the piston member 27 which carries the ball 252being displaced rearwardly when the pressure increases in the cylinderspace 45. The cylinder 21 presents a throttled outlet 46 to which acooling-water intake of the engine is intended to be connected. Aconduit to a pressure log can also be connected to the outlet 46. Thehelical spring 28 illustrated in FIG. 1 can, if necessary, be replacedby a gas spring.

The above-described compact embodiment of the drive arrangementconsisting of propulsion unit and engine allows a short intermediateshaft 50 to be used between the flywheel 51 of the engine and the drivejoints 52 of the drive shaft housing 3. The shaft does not need to besupported by an intermediate bearing, but can be coupled to the flywheel51 via an elastic joint 54 which includes an outer sleeve 55 which isnon-rotatably fastened to the flywheel, an inner sleeve 56 non-rotatablyattached to the shaft, an intermediate bush 57 vulcanised to the sleeves55, 56 and a pair of bearing rings 58 made of low friction plastics, forexample nylon.

I claim:
 1. Boat propulsion unit intended to be suspended on the outsideof a boat transom and driveably connected to an engine on the inside ofthe transom, said unit comprising a propeller drive shaft housing, asuspension arrangement intended to be fixedly secured to the transom,pivot means for pivotally connecting the drive shaft housing to thesuspension arrangement to allow pivotal displacement of the drive shafthousing relative to the suspension arrangement about a first pivot axisin a vertical plane and a second pivot axis in a horizontal plane,steering means which is arranged to effect pivotal displacement of thedrive shaft housing about said first axis, and trim and tilt means whichis arranged to effect pivotal displacement of the drive shaft housingabout said second axis, said suspension arrangement (2) including aframe member (5) which is intended to be fixed around an opening (12) ina boat transom (4), and a carrier (6) resiliently supported by the framemember and shaped so as to form a flywheel casing (20) adapted to beattached to an engine, said carrier covering the opening and supportingsaid pivot means.
 2. Boat propulsion unit according to claim 1, whereinthe carrier (6) has an edge region which projects into a slot (19a) in adamping ring (19) of flexible material, said ring being accommodated ina U-shaped channel (18) in the frame member (5).
 3. Boat propulsion unitaccording to claim 2, wherein the U-shaped channel (18) is delimited ina direction towards the inside of the transom (4) by a removablecovering ring (17).
 4. Boat propulsion unit according to claim 3,wherein the frame member (5) is provided with a T-shaped slot (13), andwherein a plurality of screws (14) accommodated within the slot (13)affixes the frame member to the transom and the covering ring (17) tothe frame member with help of yokes (15) and nuts (16).